It is proposed to identify the genomic RNAs and to study the genetic structure and gene products of retroviruses. Particular emphasis will be on the definition and specificity of the transforming onc genes and their products and functions. Two classes of onc genes will be studied, those which encode protein products unrelated to essential virion genes and those which encode hybrid proteins consisting of seuqences shared with, and sequences unrelated to, essential virion genes. Further the relationship between onc genes and cellular DNA, or possibly cellular genes, related to viral onc genes will be investigated. The techniques will include propagation and assaying of viruses in tissue culture and in some cases in animals and biochemical analysis of viral RNAs, protein and proviral DNAs. Nucleic acid analysis will involve RNA-DNA hybridization, gel electrophoresis, oligonucleotide fingerprinting and molecular cloning of DNA. Protein analysis will involve immunoprecipitation, gell electrophoresis and assays of enzymatic activities such as DNA polymerase and phosphokinases.